This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    ACK (positive) acknowledgement    BS base station    BW bandwidth    CQI channel quality information    D2D device-to-device    DL downlink (eNB towards UE)    DRX discontinuous reception    DTX discontinuous transmission    eNB E-UTRAN Node B (evolved Node B)    EPC evolved packet core    E-UTRAN evolved UTRAN (LTE)    FDD frequency division duplex    FDMA frequency division multiple access    HARQ hybrid automatic repeat-request    HSPA high speed packet access    IEEE institute of electrical and electronics engineers    LTE long term evolution of UTRAN (E-UTRAN)    LTE-A LTE advanced    MAC medium access control (layer 2, L2)    MANET mobile ad hoc network    MBMS multimedia broadcast/multicast service (3GPP)    MCS modulation and coding scheme    MM/MME mobility management/mobility management entity    NACK negative acknowledgement    Node B base station    OFDMA orthogonal frequency division multiple access    O&M operations and maintenance    PDCP packet data convergence protocol    PHY physical (layer 1, L1)    QoS quality of service    Rel release    RLC radio link control    RNTI radio network temporary identity    RRC radio resource control    RRM radio resource management    S-GW serving gateway    SC-FDMA single carrier, frequency division multiple access    TDD time division duplex    UE user equipment, such as a mobile station, mobile node or mobile terminal    UL uplink (UE towards eNB)    UTRAN universal terrestrial radio access network    Wi-Fi WLAN based on the IEEE 802.11 standard    WLAN wireless local area network
The specification of a communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.8.0 (2009-04), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8),” incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8 (with also contains 3G HSPA and its improvements). In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3GPP TS 36.300, V9.1.0 (2009-9).
FIG. 1A reproduces FIG. 4.1 of 3GPP TS 36.300 V8.8.0, and shows the overall architecture of the E-UTRAN system 2 (Rel-8). The E-UTRAN system 2 includes eNBs 3, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs 3 are interconnected with each other by means of an X2 interface. The eNBs 3 are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to a S-GW by means of a S1 interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913, V8.0.1 (2009-03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E-UTRA (LTE-Advanced) (Release 8), incorporated by reference herein in its entirety. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel. 8 radio access technologies to provide higher data rates at very low cost. LTE-A will most likely be part of LTE Rel. 10. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping the backward compatibility with LTE Rel 8.
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of Rel-8 LTE (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20 MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8.
A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.
FIG. 1B shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form M×Rel-8 BW (e.g. 5×20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) bandwidths.
MBMS includes two components: broadcast and multicast. Both portions refer to types of point-to-multipoint communication. Broadcasting is a unidirectional communication to an unknown set of receivers (i.e., the transmitting device does not need to track or maintain records regarding the receiving devices). Multicasting is a communication to a particular group of receiving devices (e.g., devices subscribed to the multicast, devices subscribed to a multicast group address). Generally, multicasting uses an efficient strategy whereby copies of the multicast transmission are created only when links to the multiple subscribers diverge. For purposes of convenience, the transmitting device of a point-to-multipoint communication (e.g., multicast, broadcast, MBMS) will be referred to as a sender or source (e.g., sender/source, source device).
As currently under consideration LTE-A may include D2D communication integrated with the cellular network. This integration would mean that the devices (e.g., UEs) could communicate via a direct (physical) communication link (e.g., using radio resources of the cellular network). As a non-limiting example, the cellular network may operate in FDD mode while the D2D connections utilize a TDD mode with cellular network UL, DL or UL and DL resources (controlled by the eNBs). Reference in regard to an integrated network having D2D and cellular communications generally may be made to PCT Publication No. WO 2005/060182 and U.S. Pat. No. 7,308,266.
The integration of D2D communications with a cellular network can be utilized to provide various improvements over conventional systems.